Folding of viral envelope glycoproteins in the endoplasmic reticulum

Viral glycoproteins fold and oligomerize in the endoplasmic reticulum of th e host cell. They employ the cellular machinery and receive assistance from cellular folding factors. During the folding process, they are retained in the compartment and their structural quality is checked by the quality con trol system of the endoplasmic reticulum. A special characteristic that dis tinguishes viral fusion proteins from most cellular proteins is the extensi ve conformational change they undergo during fusion of the viral and cellul ar membrane. Many viral proteins fold in conjunction with and dependent on a viral partner protein, sometimes even synthesized from the same mRNA. Rel evant for folding is that viral glycoproteins from the same or related viru s families may consist of overlapping sets of domain modules. The consequen ces of these features for viral protein folding are at the heart of this re view.